Multilayer capacitor

ABSTRACT

Internal dielectric layers isolated between them by a ceramic layer are arranged in a dielectric body, other internal conductor layers also isolated between them by a ceramic layer are arranged in the dielectric body by being isolated from the above internal conductor layers. Each of the all internal conductor layers is formed with a cut part, and a channel part is formed around the cut part, and the channel parts are arranged so that currents flow in mutually reverse directions between channel parts of internal conductor layers adjoining across a ceramic layer. Consequently, the equivalent serial inductance of the multilayer capacitor is largely reduced and fluctuations of a power source voltage of a CPU is made small.

CROSS-REFERENCE TO RELATED APPLICATION

This is a Division of application Ser. No. 10/798,361 filed Mar. 12,2004. The entire disclosure of the prior application is herebyincorporated by reference herein in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a multilayer capacitor wherein theequivalent serial inductance (ESL) is greatly reduced, more particularlyrelates to a multilayer ceramic capacitor capable of reducing thevoltage fluctuations of a CPU power source.

2. Description of the Related Art

In recent years, CPUs (central processing units) used for dataprocessing apparatuses have become higher in operating frequency andremarkably increased in current consumption due to the improvement inprocessing speeds and higher integration. Along with this, there is atrend toward reduction of the power consumption so as to reduce theoperating voltage. Therefore, in power sources for supplying power toCPUs, faster and larger current fluctuations occur. It has becomeextremely difficult to keep voltage fluctuations accompanying currentfluctuations to within tolerances of the power sources.

Therefore, as shown in FIG. 7, a multilayer capacitor 100 called a“decoupling capacitor” is connected to a power source 102 and frequentlyused for stabilization of the power source. Further, by fast chargingand discharging at the time of high speed, transient fluctuations incurrent, the multilayer capacitor 100 supplies current to the CPU 104and suppresses voltage fluctuations in the power source 102.

Along with the increasingly higher operating frequencies of today'sCPUs, however, the current fluctuations have become faster and larger.Therefore, the equivalent serial inductance (ESL) of the multilayercapacitor 100 itself shown in FIG. 7 becomes relatively larger. As aresult, the equivalent serial inductance greatly influences voltagefluctuations of the power source.

That is, in a conventional multilayer capacitor 100 used for the powersource circuit of the CPU 104 shown in FIG. 7, the ESL of the parasiticpart shown in the equivalent circuit of FIG. 7 is high. Thus, along withfluctuations of the current I as shown in FIG. 8, the ESL inhibits thecharging and discharging of the multilayer capacitor 100. Therefore, inthe same way as the above, the fluctuations in the voltage V of thepower source easily become greater as shown in FIG. 8, so that it willbecome impossible to handle the increasingly higher speeds of CPUs inthe future.

This is because the voltage fluctuations at the time of charging anddischarging as transition of the current are approximated by thefollowing equation 1 and therefore the level of the ESL is related tothe magnitude of fluctuation of the power source voltage:dV=ESL·di/dt  formula (1)

Here, dV is transitory fluctuation of voltage (V), “i” is the amount ofcurrent fluctuation (A), and “t” is the time of fluctuation (sec).

Here, the appearance of this conventional capacitor is shown in FIG. 9and the internal structure is shown in FIG. 10. Below, a conventionalmultilayer capacitor 100 will be explained based on these figures. Thatis, the conventional multilayer capacitor 100 shown in FIG. 9 isstructured to give an electrostatic capacity by alternately stacking apair of ceramic layers 112A each provided with one of two types ofinternal conductor layers 114 and 116 shown in FIG. 10 and forming adielectric body 112.

Further, these two types of internal conductor layers 114 and 116 areled out to mutually facing two side surfaces 112B and 112C. Further, theterminal electrode 118 connected to the internal conductor layers 114and the terminal electrode 120 connected to the internal conductor layer116 are set at the mutually facing side surfaces 112B and 112C of themultilayer capacitor 100 shown in FIG. 9.

In the conventional multilayer capacitor 100, the ESL is large and ithas been particularly difficult to reduce the voltage fluctuations ofCPU power sources.

Note that to reduce the ESL, multilayer capacitors disclosed in theJapanese Unexamined Patent Publication No. 11-144996, No. 2001-284171,No. 2002-151349, No. 2002-231559 and No. 2002-164256, etc. have beendeveloped.

However, there have been demands for multilayer capacitors capable offurthermore reducing particularly the voltage fluctuations of CPU powersources.

SUMMARY OF THE INVENTION

The present invention has as its object the provision of a multilayercapacitor capable of greatly reducing the equivalent serial inductanceand reducing the voltage fluctuations in CPU power sources.

To attain this object, the multilayer capacitor according to the presentinvention is a multilayer capacitor having dielectric layers and atleast four types of, that is, first to fourth, internal conductor layersinsulated from one another by the dielectric layer and arranged in anorder from the first to fourth ones in a dielectric body;

-   -   wherein    -   each of the first to fourth internal conductor layers is formed        with at least one cut part;    -   the internal conductor layers are formed with channel parts for        current to flow in return by the respective cut parts; and    -   the channel parts in the internal conductor layers adjoining        each other across the dielectric layer in the stacking direction        carry current flowing in the reverse directions from each other.

According to the multilayer capacitor of the first aspect of the presentinvention, when powering up the multilayer capacitor, currents flow inmutually reverse directions between adjoining channel parts above andbelow across a dielectric layer in the stacking direction. Along withthis, magnetic fluxes generated by a high frequency current flowing inthe internal conductor layers are cancelled out by each other and theparasitic inductance of the multilayer capacitor itself is reduced.Therefore, the equivalent serial inductance (ESL) is reduced.Furthermore, even in the same internal conductor layer, channel partspositioned on both sides of a curt part carry mutually reverse currents,so that the ESL is furthermore reduced from this point.

As explained above, in the multilayer capacitor according to the firstaspect of the present invention, the ESL is further reduced and theeffective inductance is greatly reduced. As a result, according to thefirst aspect of the present invention, fluctuation of a power sourcevoltage can be surely suppressed and an optimal multilayer capacitancefor a CPU power source is obtained.

Preferably, plane shapes of the first internal conductor layer and thethird internal conductor layer are symmetric each other with respect tothe center of them.

Preferably, plane shapes of the second internal conductor layer and thefourth internal conductor layer are symmetric each other with respect tothe center of them.

By forming the internal conductor layers to have the above pattern,currents are easily made to be in mutually reverse directions betweenchannel parts of internal conductor layers adjoining across a dielectriclayer in the stacking direction.

Preferably, the first internal conductor layer has a first lead part ledto a first side surface of the dielectric body; and

-   -   the third internal conductor layer has a third lead part led to        a third side surface being opposite of the first side surface of        the dielectric body.

Preferably, the first side surface of the dielectric body is attachedwith a first terminal electrode connected to the first lead part; and

-   -   the third side surface of the dielectric body is attached with a        third terminal electrode connected to the third lead part.

Preferably, the second internal conductor layer has a second lead partled to a second side surface being different from the first side surfaceand the third side surface of the dielectric body; and

-   -   the fourth internal conductor layer has a fourth lead part led        to a fourth side surface on the opposite side of the second side        surface of the dielectric body.

Preferably, the second side surface of the dielectric body is attachedwith a second terminal electrode connected to the second lead part; and

-   -   the fourth side surface of the dielectric body is attached with        a fourth terminal electrode connected to the fourth lead part.

By forming terminal electrodes respectively on the four side surfaces ofthe dielectric body as above, the ESL can be reduced.

Preferably, a width of the first lead part is substantially the samewith the entire width of the first internal conductor layer formed withthe cut part; and

-   -   a width of the third lead part is substantially the same with        the entire width of the third internal conductor layer formed        with the cut part.

Preferably, the first terminal electrode and the third terminalelectrode have the same or wider width compared with those of the firstlead part and third lead part.

By making the widths of the first lead part and third lead part wide asabove, connection of the lead parts and corresponding terminalelectrodes are furthermore ensured.

A width of the second lead part may be substantially the same as that ofthe channel part separated by the cut part of the second internalconductor layer; and

-   -   a width of the fourth lead part may be substantially the same as        that of the channel part separated by the cut part of the fourth        internal conductor layer. Note that the widths of the second and        fourth lead parts may be substantially the same as the width of        the corresponding internal conductor layer.

Preferably, the second lead part is led to the substantial centerportion of the second side surface; and

-   -   the fourth lead part is led to the substantial center of the        fourth side surface.

In the first aspect of the present invention, a width of the secondterminal electrode may be substantially the same as or wider than thatof the second lead part but narrower than that of the second sidesurface; and

-   -   a width of the fourth terminal electrode may be substantially        the same as that of the second terminal electrode.

In the first aspect of the present invention, the first to fourthinternal conductor layers may be stacked in this order repeatedly for aplurality of times in the stacking direction respectively across thedielectric layers. In this case, an electrostatic capacity of themultilayer capacitor becomes large, the effect of cancellation of themagnetic field is improved, the inductance is greatly reduced, and theESL is furthermore reduced.

According to the first aspect of the present invention, a shape of aplane of the cut part is not particularly limited but preferably is, forexample, a substantial L-shape. When in the case of the L-shaped cutpart, channel parts in mutually reverse directions are easily formed.

To attain the above object, a multilayer capacitor according to thesecond aspect of the present invention is a multilayer capacitorcomprising:

-   -   dielectric layers and    -   at least eight types of, that is, first to eight, internal        conductor layers insulated from one another by the dielectric        layer and arranged in an order from the first to eighth ones in        a dielectric body;    -   wherein    -   each of the first to eighth internal conductor layers is formed        with at least one cut part;    -   each of the internal conductor layers is formed with a channel        part for a current to flow in return by the cut part; and    -   the channel parts in the internal conductor layers adjoining        each other across the dielectric layer in the stacking direction        carry current flowing in the reverse directions from each other.

In the second aspect of the present invention, eight types of internalconductor layers respectively have cut parts, portions around the cutparts on the internal conductor layers configure channel parts, andcurrents flow in reverse directions on the same plane and flow inmutually reverse directions between channel parts of other internalconductor layers adjoining across a dielectric layer.

Accordingly, magnetic fluxes generated by a high frequency currentflowing in the internal conductor layers are cancelled out by eachother, and the parasitic inductance of the multilayer capacitor itselfcan be reduced. As a result, the equivalent serial inductance (ESL) isdecreased.

Furthermore, even in the same internal conductor layer, currents flow inmutually reverse directions between channel portions positioned on bothsides of a cut part, so that the equivalent serial inductance isfurthermore reduced.

From the above, according to the multilayer capacitor of the secondaspect of the present invention, furthermore reduced ESL can be attainedand the effective inductance is furthermore greatly reduced.

Preferably, plane shapes of the first internal conductor layer and thefifth internal conductor layer are symmetric with respect to the centerof them;

-   -   plane shapes of the second internal conductor layer and the        sixth internal conductor layer are symmetric with respect to the        center of them;    -   plane shapes of the third internal conductor layer and the        seventh internal conductor layer are symmetric with respect to        the center of them; and    -   plane shapes of the fourth internal conductor layer and the        eighth internal conductor layer are symmetric with respect to        the center of them.

By configuring the first to eighth internal conductor layers to have theabove pattern, currents in reverse directions are easily made betweenadjoining internal conductor layers in the stacking direction.

Preferably, the first internal conductor layer has a first lead part ledto the first side surface of the dielectric body;

-   -   the second internal conductor layer has a second lead part led        to a different position from the first lead part on the first        side surface of the dielectric body;    -   the fifth internal conductor layer has a fifth lead part led to        the third side surface on the opposite side of the first side        surface of the dielectric body;    -   the sixth internal conductor layer has a sixth lead part led to        a different position from the fifth lead part on the third side        surface of the dielectric body;    -   the third internal conductor layer has a third lead part led to        the second side surface being different from the first side        surface and the third side surface of the dielectric body;    -   the fourth internal conductor layer has a fourth lead part led        to a different position from the third lead part on the second        side surface of the dielectric body;    -   the seventh internal conductor layer has a seventh lead part led        to the fourth side surface on the opposite side of the second        side surface of the dielectric body; and    -   the eighth internal conductor layer has a eighth lead part led        to a different position from the seventh lead part on the fourth        side surface of the dielectric body.

Preferably, a first terminal electrode and a second terminal electroderespectively connected to the first lead part and second lead part areattached to the first side surface of the dielectric body;

-   -   a third terminal electrode and a fourth terminal electrode        respectively connected to the third lead part and fourth lead        part are attached to the second side surface of the dielectric        body;    -   a fifth terminal electrode and a sixth terminal electrode        respectively connected to the fifth lead part and sixth lead        part are attached to the third side surface of the dielectric        body; and    -   a seventh terminal electrode and an eighth terminal electrode        respectively connected to the seventh lead part and eighth lead        part are attached to the fourth side surface of the dielectric        body.

By arranging the lead parts and electrodes configured as above, twoterminal electrodes can be formed on each of the four side surfaces ofthe dielectric body. Moreover, when powering up the multilayercapacitor, polarities of adjoining terminal electrodes become mutuallydifferent to be alternately positive and negative electrodes forcurrents to flow. As a result, magnetic fluxes generated at therespective lead parts are cancelled out by each other by the currentsflowing in reverse directions in the lead parts, and the effect offurthermore reducing the equivalent serial inductance is obtained.

Preferably, a width of each of the lead parts is ⅓ to ¼ of a width ofthe channel part in each of the internal conductor layers. Due to thesizes, the configuration of arranging two terminal electrodes on oneside surface can be surely attained. Also, the respective internalconductor layers and terminal electrodes are more surely connected.

Preferably, the first to eighth internal conductor layers are stacked inthis order repeatedly for a plurality of times in the stacking directionrespectively across the dielectric layers.

In this case, not only does the electrostatic capacity of the multilayercapacitor become higher, but also the action of cancellation of themagnetic fields becomes further greater, the inductance is more greatlyreduced, and the ESL is more greatly reduced.

In the second aspect of the present invention, the plane shape of thecut part is not particularly limited, but preferably it is substantiallya linear shape. In the second aspect of the present invention, currentsflowing in mutually reverse directions are easily made even when theplane shape of the cut part is made to be substantial linear shape.

To attain the above object, the multilayer capacitor according to athird aspect of the present invention is a multilayer capacitorcomprising:

-   -   dielectric layers, and    -   at least four types of, that is, first to fourth, internal        conductor layers insulated from one another by the dielectric        layer and arranged in an order from the first to eighth ones in        a dielectric body,    -   a fifth internal conductor layer formed on the dielectric layer        formed with the first internal conductor layer, adjacent to the        first internal conductor layer on the same plane to be a pattern        isolated from the first internal layer;    -   a sixth internal conductor layer formed on the dielectric layer        formed with the second internal conductor layer, adjacent to the        second internal conductor layer on the same plane to be a        pattern isolated from the second internal layer;    -   a seventh internal conductor layer formed on the dielectric        layer formed with the third internal conductor layer, adjacent        to the third internal conductor layer on the same plane to be a        pattern isolated from the third internal layer; and    -   an eighth internal conductor layer formed on the dielectric        layer formed with the fourth internal conductor layer, adjacent        to the fourth internal conductor layer on the same plane to be a        pattern isolated from the fourth internal layer;    -   wherein    -   each of the first to eighth internal conductor layers is formed        with at least one cut part;    -   each of the internal conductor layers is formed with a channel        part for a current to flow in return by the cut part; and    -   the channel parts in the internal conductor layers adjoining        each other across the dielectric layer in the stacking direction        carry current flowing in the reverse directions from each other.

In a multilayer capacitor according to the third aspect of the resentinvention, when powering up the multilayer capacitor, currents flow inmutually reverse directions between adjoining channel parts above andbelow across a dielectric layer in the stacking direction. Along withthis, magnetic fluxes generated by a high frequency current flowing inthe internal conductor layers are cancelled out by each other and theparasitic inductance of the multilayer capacitor itself is reduced.Therefore, the equivalent serial inductance (ESL) is reduced.Furthermore, even in the same internal conductor layer, channel partspositioned on both sides of a curt part carry mutually reverse currents,so that the ESL is furthermore reduced from this point.

In the third aspect of the present invention, two out of eight types ofinternal conductor layers are respectively arranged on the same plane tobe four layers to be stacked. Therefore, inside of one dielectric body,two sets of capacitors arranged with the internal conductor layersfacing to each other and arranged in parallel are formed.

Namely, the multilayer capacitor according to the third aspect of thepresent invention exhibits the effect such that there are two adjoiningmultilayer capacitors according to the first aspect of the presentinvention in one dielectric body, and the ESL is furthermore reduced andthe effective inductance is greatly reduced. As a result, according tothe third aspect, fluctuations of a power source voltage can be surelysuppressed and an optimal multilayer capacitor for a CPU power sourcecan be obtained.

Also, in the third aspect of the present invention, eight types ofinternal conductor layers are arranged by two on the same plane tocompose a capacitor array configured by two sets of capacitors, amultilayer capacitor with higher performance can be realized.

Preferably, plane shapes of the first internal conductor layer and thethird internal conductor layer are symmetric with respect to the centerof them;

-   -   plane shapes of the second internal conductor layer and the        fourth internal conductor layer are symmetric with respect to        the center of them;    -   plane shapes of the fifth internal conductor layer and the        seventh internal conductor layer are symmetric with respect to        the center of them; and    -   plane shapes of the sixth internal conductor layer and the        eighth internal conductor layer are symmetric with respect to        the center of them.

More preferably, plane shapes of the first internal conductor layer andthe fifth internal conductor layer are symmetric with respect to thecenter of a space between them;

-   -   plane shapes of the second internal conductor layer and the        sixth internal conductor layer are symmetric with respect to the        center of a space between them;    -   plane shapes of the third internal conductor layer and the        seventh internal conductor layer are symmetric with respect to        the center of a space between them; and    -   plane shapes of the fourth internal conductor layer and the        eighth internal conductor layer are symmetric with respect to        the center of a space between them.

By forming the internal conductor layers to be the above pattern,currents are easily made to be in mutually reverse directions betweenchannel parts of internal conductor layers adjoining across a dielectriclayer in the stacking direction.

Preferably, the first internal conductor layer has a first lead part ledto the first side surface of the dielectric body;

-   -   the fifth internal conductor layer has a fifth lead part led to        the third side surface on the opposite side of the first side        surface of the dielectric body;    -   the second internal conductor layer has a second lead part led        to a different position from the first lead part on the first        side surface of the dielectric body;    -   the sixth internal conductor layer has a sixth lead part led to        a different position from the fifth lead part on the third side        surface of the dielectric body;    -   the third internal conductor layer has a third lead part led to        a different position from the fifth lead part and sixth lead        part on the third side surface of the dielectric body;    -   the seventh internal conductor layer has a seventh lead part led        to a different position from the first lead part and second lead        part on the first side surface of the dielectric body;    -   the fourth internal conductor layer has a fourth lead part led        to a different position from the third lead part, fifth lead        part and sixth lead part on the third side surface of the        dielectric body; and    -   the eighth internal conductor layer has a eighth lead part led        to a different position from the first lead part, second lead        part and seventh lead part on the first side surface of the        dielectric body.

Preferably, the first side surface of the dielectric body is attachedwith a first terminal electrode connected to the first lead part, asecond terminal electrode connected to the second lead part, a seventhterminal electrode connected to the seventh lead part and an eighthterminal electrode connected to the eighth lead part; and

-   -   the third side surface of the dielectric body is attached with a        third terminal electrode connected to the third lead part, a        fourth terminal electrode connected to the fourth lead part, a        fifth terminal electrode connected to the fifth lead part and an        sixth terminal electrode connected to the sixth lead part.

As a result, for example, lead parts of two internal conductor layersadjoining across a dielectric layer are respectively connected to twoadjoining terminal electrodes arranged on a side surface of thedielectric body. Accordingly, when powering up the multilayer capacitor,polarities of adjoining terminal electrodes become mutually different tobe alternately positive and negative electrodes for currents to flow. Asa result, magnetic fluxes generated at the respective lead parts arecancelled out by each other by the currents flowing in reversedirections in the lead parts, and the effect of furthermore reducing theequivalent serial inductance is obtained.

Preferably, each of the widths of the first to eight lead parts is thesame as or narrower than that of a channel part in the internalconductor layers. Due to the configuration, four terminal electrodes canbe arranged next to each other on each of two facing side surfaces ofthe dielectric body.

Preferably, the dielectric body has a parallelepiped shape having thesecond side surface and fourth side surface being different from thefirst side surface and third side surface; and

-   -   widths of the first side surface and third side surface are        wider than those of the second side surface and fourth side        surface.

Due to the above configuration, four of the total of eight lead partsrespectively led from the eight internal conductor layers are easily ledto each of longitudinally formed two side surfaces of the four sidesurfaces of the dielectric body. Furthermore, polarities of adjoiningterminal electrodes become mutually different. Also, since each of thelongitudinally formed two side surfaces of the four side surfaces of thedielectric element is provided with four terminal electrodes connectedto lead parts of internal conductor layers, the longitudinally formedside surfaces can be effectively utilized. Thus, the multilayercapacitor can be made compact.

Preferably, the first to fourth internal conductor layers are stacked inthis order repeatedly for a plurality of times in the stacking directionrespectively across the dielectric layers; and

-   -   the fifth to seventh internal conductor layers are stacked in        this order repeatedly for a plurality of times in the stacking        direction respectively across the dielectric layers

According to the above configuration, not only does the electrostaticcapacity of the multilayer capacitor become higher, but also the actionof cancellation of the magnetic fields becomes further greater, theinductance is more greatly reduced, and the ESL is more greatly reduced.

Preferably, the cut parts formed on the first, fifth, third and seventhinternal conductor layers have a substantial L-shape; and

-   -   the cut parts formed on the second, sixth, fourth and eighth        internal conductor layers have a substantial linear shape. When        the cut parts are formed as such, it is easy to form channel        parts in mutually reverse directions.

Preferably, in the first to third aspects of the present invention, awidth of the cut part is 1/10 to ⅓, more preferably ⅛ to ¼ of a width ofthe internal conductor layer. If the width of the cut part is toonarrow, the insulation is not enough. If the width is too wide, thesection of the conductor layer is reduced and the capacitance isreduced.

BRIEF DESCRIPTION OF DRAWINGS

Below, the present invention will be explained in detail with referenceto the attached drawings, in which:

FIG. 1 is a disassembled perspective view of a multilayer capacitoraccording to a first embodiment of the present invention showing eachpattern of internal conductor layers thereof;

FIG. 2 is a perspective view of the multilayer capacitor in FIG. 1;

FIG. 3 is a sectional view along the line III-III in FIG. 2;

FIG. 4 is a sectional view along the line IV-IV in FIG. 3;

FIG. 5 is a view of an equivalent circuit of the multilayer capacitorshown in FIG. 1 to FIG. 4;

FIG. 6 is a graph of the attenuation characteristics of examples andcomparative examples of the present invention;

FIG. 7 is an example of a circuit in which a multilayer capacitor isinstalled;

FIG. 8 is a graph of the relationship between current fluctuation andvoltage fluctuation in a circuit employing a multilayer capacitor of therelated art;

FIG. 9 is a perspective view of a multilayer capacitor according to therelated art;

FIG. 10 is a disassembled perspective view of internal conductor layersof a multilayer capacitor shown in FIG. 9;

FIG. 11 is a disassembled perspective view of the multilayer capacitoraccording to another embodiment of the present invention, showing eachpattern of internal conductor layers thereof;

FIG. 12 is a perspective view of the multilayer capacitor shown in FIG.11;

FIG. 13 is a sectional view along the line XIII-XIII in FIG. 12;

FIG. 14 is a view of an equivalent circuit of the multilayer capacitorshown in FIG. 11 to FIG. 13;

FIG. 15 is a graph of the attenuation characteristics of examples andcomparative examples of the present invention;

FIG. 16 is a disassembled perspective view of a multilayer capacitoraccording to another embodiment of the present invention, showing eachpattern of internal conductor layers thereof;

FIG. 17 is a perspective view of the multilayer capacitor shown in FIG.16;

FIG. 18 is a sectional view along the line XVIII-XVIII in FIG. 17;

FIG. 19 is a view of an equivalent circuit of the multilayer capacitorshown in FIG. 16 to FIG. 18;

FIG. 20 is a circuit diagram wherein the multilayer capacitor shown inFIG. 16 to FIG. 18 is connected to two circuits as a capacitor array;and

FIG. 21 is a view of a graph of the attenuation characteristics ofsamples according to examples and comparative examples of the presentinvention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Below, an embodiment of a multilayer capacitor according to the presentinvention will be explained based on the drawings.

First Embodiment

A multilayer ceramic capacitor as an embodiment of the multilayercapacitor according to the present invention (hereinafter simplyreferred to as a “multilayer capacitor”) 10 is shown in FIG. 1 to FIG.5. As shown in these figures, the multilayer capacitor 10 is comprisedof, as a main part, a dielectric body 12 comprised of a rectangularparallelepiped shaped sintered body obtained by sintering a stack of aplurality of ceramic green sheets as dielectric sheets (which becomeceramic layers 12A after firing).

As shown in FIG. 1, FIG. 3 and FIG. 4, a planar shaped first internalconductor layer 14, wherein the plane is along the X-axis and Y-axis, isarranged at a position of a predetermined height in the stackingdirection Z of the ceramic layers (dielectric layers) 12A in thedielectric body 12. In the dielectric body 12, the same planar shapedsecond internal conductor layer 16 is arranged below the internalconductor layer 14 over the ceramic layer 12A.

In the dielectric body 12, below the second internal conductor layer 16in the stacking direction Z is arranged the same planar shaped thirdinternal conductor layer 18 over a ceramic layer 12A. Below the internalconductor layer 18 in the stacking direction Z is arranged the sameplanar shaped fourth internal conductor layer 20. In this way, the firstinternal conductor layer 14 to the fourth internal conductor layer 20are arranged facing to each other across the ceramic layers 12A in thedielectric body 12.

Namely, in the present embodiment, by respectively sandwiching theceramic layers 12A as dielectric sheet after firing, the first internalconductor layer 14 to the fourth internal conductor layer 20 arearranged in order in the dielectric body 12. Moreover, below the fourthinternal conductor layer 20 in the stacking direction Z is, as shown inFIG. 3 and FIG. 4, a set of the four layers, the first to fourthinternal conductor layers 14 to 20 in the same order as above, isrepeatedly stacked. For example, about 100 sets (3 sets in the figures)of the first to fourth internal conductor layers 14 to 20 are arrangedin total.

The centers of these internal conductor layers 14, 16, 18 and 20 arearranged at substantially the same positions as the center of thedielectric body 12. Further, the vertical and horizontal dimensions ofthe internal conductor layers 14 to 20 are made smaller than the lengthsof the corresponding sides of the dielectric body 12. Further, as thematerials of the internal conductor layers 14, 16, 18 and 20 formed insubstantially rectangular shapes, not only may base metal materials suchas nickel, nickel alloys, copper, or copper alloys be considered, butalso materials mainly comprised of these metals may be considered.

In the present embodiment, as shown in FIG. 1, first to fourth cut parts22 a to 22 d respectively having its main parts extending in the rightand left directions with respect to the X-axis direction are provided atthe center portion of the internal conductor layers 14 to 20,respectively. These cut parts 22 a to 22 d have a substantial L-shape. Acut width W1 of the cut parts 22 a to 22 d is preferably 1/10 to ⅓, morepreferably ⅛ to ¼ of a width W0 of the internal conductors layers 14 to20.

The first cut part 22 a extends from the nearer side of the Y-axisdirection near the left side of the first internal conductor layer 14 inthe X-axis direction to the center portion of the conductor layer 14 inthe Y-axis direction along the Y-axis direction, and extends from thereto the right along the X-axis direction. The second cut portion 22 bextends from the nearer side of the Y-axis direction near the center ofthe second internal conductor layer 16 in the X-axis direction to thecenter portion of the conductor layer 16 in the Y-axis direction, andextends from there to the left in the X-axis direction.

The third cut part 22 c extends from the far side of the Y-axisdirection near the right side of the third internal conductor layer 18in the X-axis direction to the center portion of the conductor layer 18in the Y-axis direction along the Y-axis direction, and extends fromthere to the left side along the X-axis direction. The fourth cut part22 d extends from the far side of the Y-axis direction near the centerof the fourth internal conductor layer 20 in the X-axis direction to thecenter portion of the conductor layer 20 in the Y-axis direction alongthe Y-axis direction, and extends from there to the right side along theX-axis direction.

As a result that these cut portions 22 a to 22 d are formed, theinternal conductor layers 14 to 20 are formed with first to fourthchannel parts 14B to 20B for current to return and flow. Furthermore,due to the formation of these cut portions 22 a to 22 d, the firstinternal conductor layer 14 and the third internal conductor layer 18have a planar pattern shape in point symmetry with respect to the centerof these conductors. Also, the second internal conductor layer 16 andthe fourth internal conductor layer 20 have a planar pattern shape inpoint symmetry with respect to the center of these conductors.

As shown in FIG. 1, the first internal conductor layer 14 is formed witha first lead part 14A led from the left end of the internal conductorlayer 14 to the left side direction in the X-axis direction so as to beled out by the entire width W0 (the entire width in the Y-axisdirection) of the internal conductor layer 14. Also, the second internalconductor layer 16 is formed a second lead part 16A led from the centerportion on the nearer side of the Y-axis direction on its plane towardthe nearer direction.

The third internal conductor layer 18 is formed with a lead part 18A ledfrom a right-of-center portion in the X-axis direction on its plane tothe right direction by the entire width W0 of the internal conductorlayer 18. Also, the fourth internal conductor layer 20 is formed with alead part 20A led from the center portion on the far side in the Y-axisdirection on its plane to the far side direction.

As a result, wide lead parts 14A and 18A led to the first side surface12B and the third side surface 12D facing to each other on the right andleft of the X-axis in the dielectric body 12 shown in FIG. 2 areprovided to the internal conductor layers 14 and 18, respectively.Furthermore, the narrow lead parts 16A and 20A led to the second sidesurface 12C and fourth side surface 12E facing to each other on thenearer side and far side in the Y-axis direction of the dielectric body12 are provided to the two internal conductor layers 16 and 20,respectively. The width of the lead parts 16A and 20A is, for example,approximately the same as that of the channel part 16B or 20B.

As shown in FIG. 2, the first side surface 12B on the left is providedwith a first terminal electrode 24 having a size of covering the entirewidth of the side surface 12B so that the entire width of the first leadpart 14A of the first internal conductor layer 14 is connected to thefirst lead part 14A. The third side surface 12D on the right is providedwith a third terminal electrode 18 having a size of covering the entirewidth of the side surface 12D, so that the third lead part 18A of thethird internal conductor layer 18 is connected to the third lead part18A.

Also, a second side surface 12C on the nearer side is provided with asecond terminal electrode 26 to be connected to the second internalconductor layer 16 via the second lead part 16A, and a fourth sidesurface 12E on the far side is provided with a fourth terminal electrode30 to be connected to the fourth internal conductor layer 20 via thefourth lead part 20A. From the above, in the present embodiment, fourside surfaces 12B to 12E of the dielectric body 12 being the rectangularparallelepiped, that is, a hexagonal shape, have the terminal electrodes24 to 30 arranged at them, respectively.

Note that widths of the second terminal electrode 26 and the fourthterminal electrode 30 are the same as or wider than the width of thesecond lead part 16 a and the fourth lead part 20 a, but is narrowerthan the width L of the dielectric body 12 in the X-axis direction. Itis preferably ⅛ to ½ of the width L, further preferably ⅙ to ⅓ or so ofthe width L. Also, the second terminal electrode 26 and the fourthterminal electrode 30 are respectively formed at the approximate centerin the X-axis direction along the stacking direction Z on the sidesurfaces 12C and 12D of the dielectric body 12.

In the multilayer capacitor 10 of the present embodiment, as shown inFIG. 5, the internal conductor layers 14 and 16 become electrodescomposing one capacitor by connecting the terminal electrode 24, forexample, to an electrode of the CPU. Also, the terminal electrode 26 isconnected, for example, to the ground side and terminal electrodes 24and 26 thereof have mutually reverse polarities when used. In the sameway, the terminal electrodes 28 and 30 have mutually reverse polaritieswhen used, so that the internal conductor layers 18 and 20 becomeelectrodes composing one capacitor.

Therefore, for example, as shown in FIG. 2, when the terminal electrodes26 and 30 become negative electrodes at the moment the terminalelectrodes 24 and 28 become positive electrodes, currents flow along theclockwise direction in the channel parts 14B and 18B of the internalconductor layers 14 and 18 respectively connected to the terminalelectrodes 24 and 28 like the current direction shown by arrows inFIG. 1. Also, currents flow along the anticlockwise direction in thechannel parts 16B and 20B of the internal conductor layers 16 and 20respectively connected to the terminal electrodes 26 and 30.

From the above, currents flow in reverse directions from each otherbetween the channel part 14B and the channel part 16B of the internalconductor layers 14 and 16 adjoining each other across the ceramic layer12A. Similarly, currents flow in reverse directions from each otherbetween the channel part 16B and the channel part 18B of the internalconductor layers 16 and 18 adjoining each other across the ceramic layer12A. Similarly, currents flow in reverse directions from each otherbetween the channel part 18B and the channel part 20B of the internalconductor layers 18 and 20 adjoining each other across the ceramic layer12A.

Next, an operation of the multilayer capacitor 10 according to thepresent embodiment will be explained.

According to the multilayer capacitor 10 according to the presentembodiment, a pair of internal conductor layers 14 and 16 face to eachother and serve as electrodes of a capacitor arranged in parallel, and apair of internal conductor layers 18 and 20 face to each other and serveas electrodes of a capacitor arranged in parallel.

Also, in the present embodiment, when powering up the multilayercapacitor 10, currents flow in reverse directions from each otherbetween the channel parts 14B to 20B of the internal conductor layers 14to 20 adjoining one another across the ceramic layers 12A. Therefore,magnetic fluxes generated by a high frequency current flowing in theinternal conductor layers are mutually cancelled out, and the equivalentserial inductance (ESL) is reduced by reducing parasitic inductance ofthe multilayer capacitor 10 itself.

Furthermore, even in the identical internal conductor layers 14 to 20,currents flow in reverse directions from each other at each channel part14B to 20B between portions positioning by sandwiching the cut parts 22,so that the equivalent serial inductance is further decreased.

From the above, the multilayer capacitor 10 according to the presentembodiment attains further reduced ESL and widely reduced effectiveinductance. As a result, according to the present embodiment, amultilayer capacitor 10 capable of surely suppressing fluctuations of apower source voltage and being optimal as a CPU power source can beobtained.

Furthermore, in the present embodiment, since a plurality of sets of theinternal conductor layers 14 to 20 are arranged in the dielectric body12, not only heightening an electrostatic capacity of the multilayercapacitor 10, but an effect of canceling the magnetic field becomesfurthermore larger, inductance is widely reduced and the ESL is furtherreduced.

Next, by using a network analyzer, an S21 characteristic of an Sparameter is measured on each sample below, and the attenuationcharacteristic of each sample was obtained, respectively. First, thesamples will be explained. Namely, the multilayer capacitor of therelated art shown in FIG. 9, which is a general capacitor, is acomparative example 1, and the multilayer capacitor according to anembodiment shown in FIG. 2 is an example 1.

Here, constant values of an equivalent circuit were calculated so thatthe actual measured value of the attenuation characteristics matcheswith an attenuation amount of the equivalent circuit in the multilayercapacitor 100 shown in FIG. 7. It is known from data of the attenuationcharacteristics of each sample shown in FIG. 6 that an attenuationamount of the example 1 in the high frequency bandwidth of 20 MHz ormore is increased by about 15 dB comparing with that in the comparativeexample. Therefore, it was confirmed from the data that high frequencycharacteristics were improved in the example.

Note that also the calculated ESL is widely reduced to 145.2 pH in theexample 1 comparing with 845.3 pH in the comparative example 1, and theeffect of the present invention was confirmed to be proved also by thosevalues. Also, the equivalent serial resistance (ESR) was 7.8 mΩ in theexample 1 while it was 5.5 mΩ in the comparative example 1.

Dimensions of the samples used here were, as shown in FIG. 9 and FIG. 2,the length W and the length L were, in both the comparative example 2and example 2 of the invention, W=1.25 mm and L=2.0 mm. Also, anelectrostatic capacity of each sample used in the test was 1.001 μF inthe comparative example 1 and 0.968 μF in the example 1.

Note that the multilayer capacitor 10 according to the above embodimentis configured to have two sets, that is four types in total, of internalconductor layers, but the number of layers is not limited to the numberexplained in the embodiment and may be larger.

Second Embodiment

Below, a multilayer capacitor accordance to a second embodiment of thepresent invention will be explained based on the drawings. Themultilayer ceramic capacitor (hereinafter, simply referred to as amultilayer capacitor) 210 according to the present embodiment is shownin FIG. 11 to FIG. 14. As shown in these figures, the multilayercapacitor 210 is comprised of, as a main part, a dielectric body 212comprised of a rectangular parallelepiped shaped sintered body obtainedby sintering a stack of a plurality of ceramic green sheets asdielectric sheets (which become ceramic layers 212A after firing).

As shown in FIG. 11 and FIG. 13, a planar shaped first internalconductor layer 221, wherein the plane is along the X-axis and Y-axis,is arranged at a position of a predetermined height of the dielectricbody 212. In the dielectric body 212, the same planar shaped secondinternal conductor layer 222 is arranged below the first internalconductor layer 221 in the stacking direction Z over the ceramic layer(dielectric layer) 212A.

In the dielectric body 212, below the second internal conductor layer222 in the stacking direction Z is arranged the same planar shaped thirdinternal conductor layer 223 over a ceramic layer 212A. Below the thirdinternal conductor layer 223 in the stacking direction Z is arranged thesame planar shaped fourth internal conductor layer 224 over a ceramiclayer 212A in the dielectric body 212.

In the same way, a fifth internal conductor layer 225, a sixth internalconductor layer 226, a seventh internal conductor layer 227 and aneighth internal conductor layer 228 formed to be a planar shape aresuccessively arranged separated by the ceramic layers 212A,respectively. Consequently, eight types of internal conductor layersfrom the internal conductor layer 221 to the internal conductor layer228 are arranged to face to each other while separated by the ceramiclayers 212A.

Namely, in the present embodiment, by sandwiching the ceramic layers212A to be dielectric sheets after firing, the first internal conductorlayer 221 to the eighth internal conductor layer 228 are arranged inorder in the dielectric body 212. Furthermore, below the eighth internalconductor layer 228, for example, a total of several tens of sets (twosets in the figure) of the internal conductor layers as an eight-layerelectrode are arranged by repeating the same order as above as shown inFIG. 13.

Namely, the centers of these internal conductor layers 221 to 228 arearranged at substantially the same positions as the center of thedielectric body 212. Further, the vertical and horizontal dimensions ofthe internal conductor layers 221 to 228 are made smaller than thelengths of the corresponding sides of the dielectric body 212. Further,as the materials of the internal conductor layers 221 to 228 formed insubstantially rectangular shapes, not only may base metal materials suchas nickel, nickel alloys, copper, or copper alloys be considered, butalso materials mainly comprised of these metals may be considered.

As shown in FIG. 11, the first internal conductor layer 221 and theeighth internal conductor layer 228 are respectively formed a first cutpart 229A1 and an eighth cut part 229A2 extending from the centerportion in the Y-axis direction on the left side in the X-axis directionto the center portion along the X-axis direction. Also, the secondinternal conductor layer 222 and the third internal conductor layer 223are respectively formed a second cut part 229B1 and a third cut part229B2 extending from the center portion in the X-axis direction on thefar side in the Y-axis direction to the center portion along the Y-axisdirection.

Also, the fourth internal conductor layer 224 and the fifth internalconductor layer 225 are respectively formed a fourth cut part 229C1 anda fifth cut part 229C2 extending from the center portion in the Y-axisdirection on the right side in the X-axis direction to the centerportion along the X-axis direction. Also, the sixth internal conductorlayer 226 and the seventh internal conductor layer 227 are respectivelyformed a sixth cut part 229D1 and a seventh cut part 229D2 extendingfrom the center portion in the X-axis direction on the nearer side ifthe Y-axis direction to the center portion along the Y-axis direction.

In the present embodiment, the planar shape of these cut parts have asubstantial linear shape extending from the center of the end portion inthe X-axis direction or the Y-axis direction in each internal conductorlayer to the center portion thereof. A width of the cut parts is thesame as that in the first embodiment.

As a result that these cut portions 229A1 to 229D2 are formed, theinternal conductor layers 221 to 228 are formed with first to eighthchannel parts 221B to 228B for current to return and flow. Furthermore,due to the formation of these cut portions 229A1 to 229D2, the firstinternal conductor layer 221 and the fifth internal conductor layer 225have a planar pattern shape in point symmetry with respect to the centerof them. Also, the second internal conductor layer 222 and the sixthinternal conductor layer 226 have a planar pattern shape in pointsymmetry with respect to the center of them.

Also, the third internal conductor layer 223 and the seventh internalconductor layer 227 have a planar pattern shape in point symmetry withrespect to the center of them. Also, the fourth internal conductor layer224 and the eighth internal conductor layer 228 have a planar patternshape in point symmetry with respect to the center of them.

As shown in FIG. 11 and FIG. 12, the first internal conductor layer 221has a first lead part 221A led to the first side surface 212B of thedielectric body 212. The second internal conductor layer 222 has asecond lead part 222A lead to a different position from the first leadpart 221A on the first side surface 212B of the dielectric body 212.

Also, the fifth internal conductor layer 225 has a fifth lead part 225Aled to the third side surface 212D on the opposite side of the firstside surface 212B of the dielectric body 212. The sixth internalconductor layer 226 has a sixth lead part 226A led to at a differentposition from the fifth lead part 225A on the third side surface 212D ofthe dielectric body 212.

The third internal conductor layer 223 has a third lead part 223A ledtoward the second side surface 212C being different from the first sidesurface 212B and the third side surface 212D of the dielectric body 212.The fourth internal conductor layer 224 has a fourth lead part 224A ledto at a different position from the third lead part 223A on the secondside surface 212C of the dielectric body 212.

The seventh internal conductor layer 227 has a seventh lead part 227Aled to the fourth side surface 212E on the opposite side of the secondside surface 212C of the dielectric body 212. The eighth internalconductor layer 228 has an eighth lead part 228A led to at a differentposition from the seventh lead part 227A on the fourth side surface 212Eof the dielectric body 212.

A width D2 of the lead parts 221A to 228A is ⅓ to ¼ of a width of thechannel portions 221B to 228B in the respective internal conductorlayers.

As shown in FIG. 12, the first side surface 212B of the dielectric body212 is attached with a first terminal electrode 231 and a secondterminal electrode 232 respectively connected to the first lead part221A and the second lead part 222A. The second side surface 212C of thedielectric body 212 is attached with a third terminal electrode 233 anda fourth terminal electrode 234 respectively connected to the third leadpart 223A and the fourth lead part 224A.

The third side surface 212D of the dielectric body 212 is attached witha fifth terminal electrode 235 and a sixth terminal electrode 236respectively connected to the fifth lead part 225A and the sixth leadpart 226A. The fourth side surface 212E of the dielectric body 212 isattached with a seventh terminal electrode 237 and a eighth terminalelectrode 238 respectively connected to the seventh lead part 227A andthe eighth lead part 228A.

Namely, two of the lead parts 221A to 228A shown in FIG. 11 are ledrespectively to each of the four side surfaces 212B to 212E of thedielectric body 212 shown in FIG. 12 and connected to terminalelectrodes 231 to 238, respectively. A width of the terminal electrodes231 to 238 is the same as or more than the width D2 of the lead parts221A to 228A shown in FIG. 11 and is determined so that the terminalelectrodes adjoining each other are insulated.

As explained above, in the present embodiment, each of the four sidesurfaces 212B to 212E of the dielectric body 212 in a parallelepipedhexahedron shape is arranged two of the terminal electrodes 231 to 238,respectively, and the eight internal conductor layers 221 to 228 and theterminal electrodes 231 to 238 are connected via the lead parts 221A to228A, respectively.

In the multilayer capacitor 210 according to the present embodiment, forexample as shown in FIG. 14, terminal electrodes 231, 233, 235 and 237are connected, for example, to electrodes of a CPU, and every otherterminal electrodes 232, 234, 236 and 238 are connected, for example, tothe ground side. Therefore, the terminal electrodes 231, 233, 235 and237 and the terminal electrodes 232, 234, 236 and 238 are applied withvoltages having reverse polarities.

As a result, for example as shown in FIG. 12 and FIG. 14, the everyother terminal electrodes 231, 233, 235 and 237 become positiveelectrodes, while the every other terminal electrodes 232, 234, 236 and238 become negative electrodes. At this time, currents flow in thedirection indicated by arrows in FIG. 11.

Namely, currents flow in the clockwise direction in the channel parts221B, 223B, 225B and 227B of the internal conductor layers 221, 223, 225and 227 respectively connected to the terminal electrodes 231, 233, 235and 237. Also, currents flow in the anticlockwise direction in thechannel parts 222B, 224B, 226B and 228B of the internal conductor layers222, 224, 226 and 228 respectively connected to the terminal electrodes232, 234, 236 and 238.

As explained above, currents in the mutually reverse directions flow inthe channel part 221B and the channel part 222B of the internalconductor layers 221 and 222 adjoining across a ceramic layer 212A. Inthe same way, currents in mutually reverse directions flow in thechannel part 222B and the channel part 223B of the internal conductorlayers 222 and 223 adjoining across a ceramic layer 212A.

In the same way, between the channel part 223B and the channel part 224Bof the internal conductor layers 223 and 224 adjoining across a ceramiclayer 212A, between the channel part 224B and the channel part 225B ofthe internal conductor layers 224 and 225 adjoining across a ceramiclayer 212A, between the channel part 225B and the channel part 226B ofthe internal conductor layers 225 and 226 adjoining across a ceramiclayer 212A, between the channel part 226B and the channel part 227B ofthe internal conductor layers 226 and 227 adjoining across a ceramiclayer 212A, between the channel part 227B and the channel part 228B ofthe internal conductor layers 227 and 228 adjoining across a ceramiclayer 212A, and between the channel part 228B and the channel part 221Bof the internal conductor layers 228 and 221 adjoining across a ceramiclayer 212A, currents in mutually reverse directions flow.

Next, an operation of the multilayer capacitor 210 according to thepresent embodiment will be explained.

According to the multilayer capacitor 210 according to the presentembodiment, when powering up the multilayer capacitor 210, currents flowas polarities of adjoining terminal electrodes become different to eachother to be alternately a positive electrode and a negative electrode inthe terminal electrodes 231 to 238. Thus, magnetic fluxes generated inthe lead parts 221A to 228A are cancelled out as a result that currentsin reverse directions flow between adjoining lead parts, and the effectof reducing the equivalent serial inductance is obtained.

Furthermore, in the present embodiment, when powering up the multilayercapacitor 210, currents flow in reverse directions from each otherbetween the channel parts of internal conductor layers adjoining acrossa ceramic layer 212A in the channel parts 221B to 228B of the internalconductor layers 221 to 228. Along with this, the magnetic fluxesgenerated by the high frequency current flowing in the internalconductor layers are canceled out. By reducing the parasitic inductanceof the multilayer capacitor 10 itself, the equivalent serial inductance(ESL) is furthermore reduced.

Further, even in the same internal conductor layers 221 to 228, thecurrent flowing directions become reverse respectively between the partspositioned across the cut parts 229A to 229D of the channel parts 221Bto 228B. Thus, the equivalent serial inductance is furthermore reduced.

From the above, in the multilayer capacitor 210 according to the presentembodiment, the ESL is widely reduced and the effective inductance iswidely reduced. As a result, according to the present embodiment,fluctuations of a power source voltage can be surely suppressed and amultilayer capacitor 210 most suitable to the CPU power source isobtained.

Furthermore, in the present embodiment, since the eight types ofinternal conductor layers 221 to 228 are arranged by the number of twoor more each in the dielectric body 212, not only does the electrostaticcapacity of the multilayer capacitor 210 become higher, but also theaction of cancellation of the magnetic fields becomes further greater,the inductance is more greatly reduced, and the ESL is more greatlyreduced.

Next, by using a network analyzer, the Szl characteristic of an Sparameter of each sample below was measured and the attenuationcharacteristics of each sample were obtained. First, each sample will beexplained. Namely, the multilayer capacitor shown in FIG. 9 as a generalcapacitor is a comparative example 2, and the multilayer capacitoraccording to the embodiment shown in FIG. 12 is an example 2.

Here, the constants of the equivalent circuit were calculated so thatthe measured value of the attenuation characteristic and the amount ofattenuation of the equivalent circuit in the multilayer capacitor 100shown in FIG. 7 matched. Further, from the data of the attenuationcharacteristics of the samples shown in FIG. 15, it is learned that aresonance point of the example 2 becomes 15 MHz from 4.5 MHz of thecomparative example 2, and an attenuation amount of the example 2 at afrequency of 15 MHz or more is increased by about 15 dB compared withthat of the comparative example 2. Therefore, from the data, it can beunderstood that improvement of the high frequency characteristics isseen in the example.

Also, the result of the ESL obtained by measuring with an impedanceanalyzer and calculating was widely reduced to 105.2 pH in the example 2compared with 845.3 pH of the comparative example 2. Note that theequivalent serial resistance (ESR) was 5.5 mΩ in the comparative example2 and 8.2 mΩ in the example 2.

Here, relating to the dimensions of the samples used, as shown in FIG. 9and FIG. 12, the length W and the length L were, in both the comparativeexample 2 and example 2 of the invention, W=1.25 mm and L=2.0 mm.Further, the electrostatic capacities of the samples used for the testswere 1.00 μF for the comparative example 2 and 0.98 μF for the exampleof the invention.

Note that the multilayer capacitor 210 according to the presentembodiment is configured to have eight types of internal conductorlayers, but the number of the layers is not limited to the numberexplained in the embodiment and may be a larger number. Also, in theabove embodiment, adjoining terminal electrodes had mutually reversepolarities, and along with this, the internal conductor layers arearranged so that mutually facing terminal electrodes have reversepolarities in the above embodiment.

Third Embodiment

A multilayer ceramic capacitor (hereinafter, simply referred to as amultilayer capacitor) 310 as a third embodiment of the multilayercapacitor according to the present invention is shown in FIG. 16 to FIG.21. As shown in the figures, the multilayer capacitor 310 is comprisedof, as a main part, a dielectric body 312 comprised of a rectangularparallelepiped shaped sintered body obtained by sintering a stack of aplurality of ceramic green sheets as dielectric sheets (which becomeceramic layers 312A after firing).

As shown in FIG. 16 and FIG. 18, a planar shaped first internalconductor layer 321, wherein the plane is along the X-axis and Y-axis,is arranged at a position of a predetermined height in the stackingdirection Z of the ceramic layers (dielectric layers) 312A in thedielectric body 312. On the ceramic layer 312A to be formed a firstconductor layer 321, a fifth internal conductor layer 325 is formedadjacent to the first internal conductor layer 321 by being insulatedwith the first internal conductor layer 321 and leaving a predeterminedspace in the X-axis direction on the same plane.

Below the first internal conductor layer 321 and the fifth internalconductor layer 325 in the Z-axis direction is formed is formed, bysandwiching a ceramic layer 312A, a second internal conductor layer 322and a sixth internal conductor layer 326 having corresponding patternsto those of the first internal conductor layer 321 and the fifthinternal conductor layer 325, respectively.

Below the second internal conductor layer 322 and the sixth internalconductor layer 326 in the Z-axis direction is formed, by sandwiching aceramic layer 312A, a third internal conductor layer 323 and a seventhinternal conductor layer 327 having corresponding patterns to those ofthe second internal conductor layer 322 and the sixth internal conductorlayer 326, respectively.

Below the third internal conductor layer 323 and the seventh internalconductor layer 327 in the Z-axis direction is formed, by sandwiching aceramic layer 312A, a fourth internal conductor layer 324 and a eighthinternal conductor layer 328 having corresponding patterns to those ofthe third internal conductor layer 323 and the seventh internalconductor layer 327, respectively.

Below the fourth internal conductor layer 324 and the eighth internalconductor layer 328 in the Z-axis direction is, by sandwiching a ceramiclayer 312A, in the same way as the above, a plurality of sets of a firstto fourth internal conductor layers 321 to 324 and the fifth to eighthinternal conductor layers 325 to 328 arranged in this order. As thematerials of the internal conductor layers 325 and 328, not only maybase metal materials such as nickel, nickel alloys, copper, or copperalloys be considered, but also materials mainly comprised of thesemetals may be considered.

At least one of cut parts 329A1 to 329D2 is formed on the first toeighth internal conductor layers 321 to 328, and the internal conductorlayers are formed channel parts 321B to 328B for current to return andflow by the cut portions, respectively.

In the present embodiment, the cut parts 329A1, 329C2, 329C1 and 329A1formed on the first, fifth, third and seventh internal conductor layers321 325, 323 and 327 have a substantial L-shape. Also, the cut parts329B1, 329D2, 329D1 and 329B2 formed on the second, sixth, fourth andeighth internal conductor layers 322 326, 324 and 328 have a substantiallinear shape.

The cut parts 329A1 and 329A2 have the same pattern, the cut parts 329B1and 329B2 have the same pattern, the cut parts 329C1 and 329C2 have thesame pattern and the cut parts 329D1 and 329D2 have the same pattern.

The cut parts 329A1 to 329D2 are formed to have the symmetricalrelationship as explained below between the internal conductor layers.Namely, the first internal conductor layer 321 and the third internalconductor layer 323 have a symmetric plane pattern with respect to thecenter of them. Also, the second internal conductor layer 322 and thefourth internal conductor layer 324 have a symmetric plane pattern withrespect to the center of them.

The fifth internal conductor layer 325 and the seventh internalconductor layer 327 have a symmetric plane pattern with respect to thecenter of them. The sixth internal conductor layer 326 and the eighthinternal conductor layer 328 have a symmetric plane pattern with respectto the center of these conductors.

Furthermore, the first internal conductor layer 321 and the fifthinternal conductor layer 325 have a symmetric plane pattern with respectto the center of a space between them. The second internal conductorlayer 322 and the sixth internal conductor layer 326 have a symmetricplane pattern with respect to the center of a space between them.

The third internal conductor layer 323 and the seventh internalconductor layer 327 have a symmetric plane pattern with respect to thecenter of a space between them. The fourth internal conductor layer 324and the eighth internal conductor layer 328 have a symmetric planepattern with respect to the center of a space between them.

By providing the cut parts 329A1 to 329D2 to the internal conductorlayers to form the above plane pattern shapes, currents in mutuallyreverse directions flow between channel parts of internal conductorlayers adjoining across a ceramic layer (dielectric layer) 312A in thestacking direction Z. Furthermore, currents also flow in mutual reversedirections between adjoining internal conductor layers positioned on thesame plane.

The first internal conductor layer 321 has a first lead part 321A led tothe first side surface 312B of the dielectric body 312 shown in FIG. 17.The fifth internal conductor layer 325 has a fifth lead part 325B led tothe third side surface 312D on the opposite side of the first sidesurface 312B of the dielectric body 312.

The second internal conductor layer 322 has a second lead part 322A ledto the first side surface 312B of the dielectric body 312. The sixthinternal conductor layer 326 has a sixth lead part 326B led to adifferent position from the fifth lead part of the dielectric body 312on the third side surface 312D.

The third internal conductor layer 323 has a third lead part 323A led toa different position from the fifth lead part 325A and the sixth leadpart 326A on the third side surface 312D of the dielectric body 312. Theseventh internal conductor layer 327 has a seventh lead part 327A led toa different position from the first lead part 321A and the second leadpart 322A on the first side surface 312B of the dielectric body 312.

The fourth internal conductor layer 324 has a fourth lead part 324A ledto a different position from the third lead part 323A, the fifth leadpart 325A and the sixth lead part 326A on the third side surface 312D ofthe dielectric body 312. The eighth internal conductor layer 328 has aeighth lead part 328A led to a different position from the first leadpart 321A, the second lead part 322A and seventh lead part 327A on thefirst side surface 312B of the dielectric body 312.

The first side surface 312B of the dielectric body 312 is attached witha first terminal electrode 331 connected to the first lead part 321A, asecond terminal electrode 332 connected to the second lead part 322A, aseventh terminal electrode 337 connected to the seventh lead part 327A,and an eighth terminal electrode 338 connected to the eighth lead part328A.

The third side surface 312D of the dielectric body 312 is attached witha third terminal electrode 333 connected to the third lead part 323A, afourth terminal electrode 334 connected to the fourth lead part 324A, afifth terminal electrode 335 connected to the fifth lead part 325A, andan sixth terminal electrode 336 connected to the sixth lead part 326A.

Four of the terminal electrodes 331 to 338 are respectively formed onlyon two facing side surfaces 312B and 312D on the longitudinal sides ofthe dielectric body 312. Adjoining terminal electrodes are away fromeach other and insulated. The second side surface 312C and the fourthside surface 312E are not formed with any terminal electrodes.

The multilayer capacitor 310 of the present embodiment is an elementincorporating two capacitors, and, for example, a use example of acircuit diagram shown in FIG. 20 is considered. Specifically, terminalelectrodes 331, 332, 333 and 334 on the left side in FIG. 20 areconnected to the power source 341 and the CPU 343 on the left side.Namely, the terminal electrodes 331 and 333 are connected between oneend side of the CPU 343 and the power source 341, and the terminalelectrodes 332 and 334 are connected to the other side of the CPU 343and also grounded.

Furthermore, the terminal electrodes 335, 336, 337 and 338 on the rightside in FIG. 20 are connected to the power source 342 and the CPU 344 onthe right side. Namely, the terminal electrodes 335 and 337 areconnected between one end side of the CPU 344 and the power source 342,and the terminal electrodes 336 and 338 are connected to the other endside of the CPU 344 and also grounded.

Therefore, as shown in the equivalent circuit shown in FIG. 19, theterminal electrodes 331, 333, 335 and 337 are used in a reverse polarityfrom that of the terminal electrodes 332, 334, 336 and 338. For example,as shown in FIG. 17 and FIG. 19, every other terminal electrodes 331 and337 on the side surface 312B on the nearer side become positiveelectrodes, and every other terminal electrodes 332 and 338 becomenegative electrodes. Also, every other electrodes 333 and 335 on theside surface 312D on the far side become positive electrodes, and everyother terminal electrodes 334 and 336 become negative electrodes. Atthis time, currents flow in the directions indicated by arrows in FIG.16.

Namely, currents flow clockwise in the channel parts 321B, 323B, 325Band 327B of the internal conductor layers 321, 323, 325 and 327respectively connected to the terminal electrodes 331, 333, 335 and 337.Also, currents flow anticlockwise in the channel parts 322B, 324B, 326Band 328B of the internal conductor layers 322, 324, 326 and 328respectively connected to the terminal electrodes 332, 334, 336 and 338.

From the above, in the left side portion of the dielectric body 312,currents flow in mutually reverse directions between the channel part321B and the channel part 322B of the internal conductor layers 321 and322 adjoining across a ceramic layer 312A. In the same way, currentsflow in mutually reverse directions between the channel part 322B andthe channel part 323B of the internal conductor layers 322 and 323adjoining across a ceramic layer 312A.

In the same way, currents flow in mutually reverse directions betweenthe channel part 323B and the channel part 324B of the internalconductor layers 323 and 324 adjoining across a ceramic layer 312A, andbetween the channel part 324B and the channel part 321B of the internalconductor layers 324 and 321.

Also, in the internal conductor layers 325 to 328 in the right sideportion of the dielectric body 312, currents flow in mutually reversedirections in the internal conductor layers adjoining across a ceramiclayer 312A.

Next, an operation of the multilayer capacitor 310 according to thepresent embodiment will be explained.

According to the multilayer capacitor 310 according to the presentembodiment, two types of terminal electrodes are respectively arrangedon the same plane from the eight types of internal conductor layers 321to 328 connected respectively to the eight terminal electrodes 331 to338. Also, in the present embodiment, two sets of capacitors arranged inparallel are formed as a result that the internal conductor layers faceto each other.

As a result, when powering up the multilayer capacitor 310 according tothe present embodiment, in the terminal electrodes 331 to 338,polarities become different from each other to be alternately positiveand negative electrodes between adjoining terminal electrodes on thesame side surface as currents flow. Along with this, magnetic fluxesgenerated respectively in the lead parts 321A to 328A are cancelled outby the currents flowing in reverse directions between adjoining leadparts, and the effect of reducing the equivalent serial inductance isobtained.

Also, when powering up the multilayer capacitor 310, between the channelparts 321B to 324B of the internal conductor layers 321 to 324 adjoiningacross ceramic layers 312A, and between the channel parts 325B to 328Bof the internal conductor layers 325 to 328, currents flow in mutuallyreverse directions. Along with this, magnetic fluxes generated by highfrequency currents flowing in the internal conductor layers arecancelled out by each other. By reducing the parasitic inductance of themultilayer capacitor 310 itself, the equivalent serial inductance (ESL)is furthermore reduced.

Further, even in the same internal conductor layers 321 to 328, currentflowing directions become reverse respectively between the partspositioned across the cut parts 329A to 329D of the channel parts 321Bto 328B. Thus, the equivalent serial inductance is furthermore reduced.

From the above, in the multilayer capacitor 310 according to the presentembodiment, the ESL is widely reduced and the effective inductance iswidely reduced. As a result, according to the present embodiment,fluctuations of a power source voltage can be surely suppressed and amultilayer capacitor 310 most suitable to the CPU power source isobtained.

Furthermore, in the present embodiment, two or more of the eight typesof internal conductor layers 321 to 328 are arranged on the same plane,respectively, to configure a capacitor array comprising two sets ofcapacitors. Therefore, a multilayer capacitor 310 having higherperformance can be realized. Since four terminal electrodes connected tothe lead parts of the internal conductor layers are provided on two sidesurfaces 312B and 312D formed to be long among the four side surfaces312B to 312E of the dielectric body 312, the two long side surfaces 312Band 312D can be effectively utilized. Therefore, the multilayercapacitor 310 can be also made compact.

Furthermore, in the present embodiment, since the eight internalconductor layers 321 to 328 are arranged by the number of two or moreeach in the dielectric body 312, so not only does the electrostaticcapacity of the multilayer capacitor 310 become higher, but also theaction of cancellation of the magnetic fields becomes further greater,the inductance is more greatly reduced, and the ESL is more greatlyreduced.

Next, by using a network analyzer, the Szl characteristic of an Sparameter of each sample below was measured and the attenuationcharacteristics of each sample were obtained. First, each sample will beexplained. Namely, the multilayer capacitor shown in FIG. 9 as a generalcapacitor is a comparative example 3, and the multilayer capacitoraccording to the embodiment shown in FIG. 17 is an example 3.

Here, the constants of the equivalent circuit were calculated so thatthe measured value of the attenuation characteristic matches with theamount of attenuation of the equivalent circuit in the multilayercapacitor 100 shown in FIG. 7. Further, from the data of the attenuationcharacteristics of the samples shown in FIG. 21, it is learned that aresonance point of the example 3 becomes high as 43 MHz or so from 18MHz or so of the comparative example 3, and an attenuation amount of theexample 3 at a frequency of 40 MHz or more is increased by about 15 dBcompared with that of the comparative example 3. Therefore, from thedata, it can be understood that improvement of the high frequencycharacteristics is seen in the example.

Note that the result of the ESL obtained by measuring with an impedanceanalyzer and calculating was widely reduced to 135.2 pH in the example 3compared with 750.5 pH of the comparative example 3. Note that theequivalent serial resistance (ESR) was 20.5 mΩ in the comparativeexample 3 and 24.8 mΩ in the example 3.

Here, relating to the dimensions of the samples used, as shown in FIG.17 and FIG. 9, the length W and the length L were, in both of thecomparative example 3 and example 3 of the invention, W=1.25 mm andL=2.0 mm. Further, the electrostatic capacities of the samples used forthe tests were 0.105 μF for the comparative example 3 and 0.102 μF forthe example 3.

Note that the multilayer capacitor 310 according to the presentembodiment is configured to have eight types of internal conductorlayers, but the number of the layers is not limited to the numberexplained in the embodiment and may be a larger number. Also, in theabove embodiment, adjoining terminal electrodes had mutually reversepolarities, and along with this, the internal conductor layers arearranged so that mutually facing terminal electrodes have reversepolarities in the above embodiment.

Note that the present invention is not limited to the above embodimentsand may be variously modified within the scope of the present invention.

1. A multilayer capacitor comprising: dielectric layers, and at leastfour types of, that is, first to fourth, internal conductor layersinsulated from one another by said dielectric layer and arranged in anorder from the first to eighth ones in a dielectric body, a fifthinternal conductor layer formed on the dielectric layer formed with saidfirst internal conductor layer, adjacent to said first internalconductor layer on the same plane to be a pattern isolated from saidfirst internal layer; a sixth internal conductor layer formed on thedielectric layer formed with said second internal conductor layer,adjacent to said second internal conductor layer on the same plane to bea pattern isolated from said second internal layer; a seventh internalconductor layer formed on the dielectric layer formed with said thirdinternal conductor layer, adjacent to said third internal conductorlayer on the same plane to be a pattern isolated from said thirdinternal layer; and an eighth internal conductor layer formed on thedielectric layer formed with said fourth internal conductor layer,adjacent to said fourth internal conductor layer on the same plane to bea pattern isolated from said fourth internal layer; wherein each of saidfirst to eighth internal conductor layers is formed with at least onecut part; each of said internal conductor layers is formed with achannel part for a current to flow in return by said cut part; and thechannel parts in said internal conductor layers adjoining each otheracross said dielectric layer in the stacking direction carry currentflowing in the reverse directions from each other.
 2. The multilayercapacitor as set forth in claim 1, wherein plane shapes of said firstinternal conductor layer and said third internal conductor layer aresymmetric each other with respect to the center of them; plane shapes ofsaid second internal conductor layer and said fourth internal conductorlayer are symmetric each other with respect to the center of them; planeshapes of said fifth internal conductor layer and said seventh internalconductor layer are symmetric each other with respect to the center ofthem; and plane shapes of said sixth internal conductor layer and saideighth internal conductor layer are symmetric each other with respect tothe center of them.
 3. The multilayer capacitor as set forth in claim 1,wherein plane shapes of said first internal conductor layer and saidfifth internal conductor layer are symmetric each other with respect tothe center of a space between them; plane shapes of said second internalconductor layer and said sixth internal conductor layer are symmetriceach other with respect to the center of a space between them; planeshapes of said third internal conductor layer and said seventh internalconductor layer are symmetric each other with respect to the center of aspace between them; and said fourth internal conductor layer and saideighth internal conductor layer are symmetric each other with respect tothe center of a space between them.
 4. The multilayer capacitor as setforth in claim 1, wherein said first internal conductor layer has afirst lead part led to the first side surface of said dielectric body;said fifth internal conductor layer has a fifth lead part led to thethird side surface on the opposite side of the first side surface ofsaid dielectric body; said second internal conductor layer has a secondlead part led to a different position from said first lead part on thefirst side surface of said dielectric body; said sixth internalconductor layer has a sixth lead part led to a different position fromsaid fifth lead part on the third side surface of said dielectric body;said third internal conductor layer has a third lead part led to adifferent position from said fifth lead part and sixth lead part on thethird side surface of said dielectric body; said seventh internalconductor layer has a seventh lead part led to a different position fromsaid first lead part and second lead part on the first side surface ofsaid dielectric body; said fourth internal conductor layer has a fourthlead part led to a different position from said third lead part, fifthlead part and sixth lead part on the third side surface of saiddielectric body; and said eighth internal conductor layer has a eighthlead part led to a different position from said first lead part, secondlead part and seventh lead part on the first side surface of saiddielectric body.
 5. The multilayer capacitor as set forth in claim 4,wherein a width of each of said first to eighth lead parts is the sameas or narrower than that of the channel part in each of said internalconductor layers.
 6. The multilayer capacitor as set forth in claim 4,wherein said dielectric body has a parallelepiped shape having saidsecond side surface and fourth side surface being different from saidfirst side surface and third side surface; and widths of the first sidesurface and third side surface are wider than those of said second sidesurface and fourth side surface.
 7. The multilayer capacitor as setforth in claim 6, wherein the first side surface of said dielectric bodyis attached with a first terminal electrode connected to said first leadpart, a second terminal electrode connected to said second lead part, aseventh terminal electrode connected to said seventh lead part and aneighth terminal electrode connected to said eighth lead part; and thethird side surface of said dielectric body is attached with a thirdterminal electrode connected to said third lead part, a fourth terminalelectrode connected to said fourth lead part, a fifth terminal electrodeconnected to said fifth lead part and an sixth terminal electrodeconnected to said sixth lead part.
 8. The multilayer capacitor as setforth in claim 1, wherein said first to fourth internal conductor layersare stacked in this order repeatedly for a plurality of times in thestacking direction respectively across said dielectric layers; and saidfifth to seventh internal conductor layers are stacked in this orderrepeatedly for a plurality of times in the stacking directionrespectively across said dielectric layers.
 9. The multilayer capacitoras set forth in claim 1, wherein said cut parts formed on said first,fifth, third and seventh internal conductor layers have a substantialL-shape; and said cut parts formed on said second, sixth, fourth andeighth internal conductor layers have a substantial linear shape. 10.The multilayer capacitor as set forth in claim 9, wherein a width ofsaid cut part is 1/10 to ⅓ of a width of said internal conductor layer.